Radio steering control



June 11, 1935. 1 BROCKSTEDT- 2,004,460

RADIO STEERING CONTROL Original Filed Au 28. 1930 INVENTOR fit l tages"f md a 7 V v In the use of vibrating reeds for special purv r IPatented June 11, i935 UNIT D STATES .aAnIo s'rnnanvc coNTitoi.Theophile E. Brockstedt, San Francisco, Calif.,

assignor 'to Washingtonlnstitute a corp'orationof Delaware August 28,1930, Serial Renewed April" 17, 1935 ogy, Inc.,

Application This'inventlon relates to signal apparatus designed toaccomplish the automatic steering of marine v'emels and airplanes byradio control and this specification is in part a continuation of an Iapplication entitled Radio signal apparatus and methods, Serial No.151,915, Filed: Dec.1, 1926, Patent No. 1,865,826.

An object of the 'strument arranged for operation with the doublemodulation type directive radio beacon, described in the aboveidentified patent and also described in another copending application,Serial 478,497, entitled Method of, and apparatus for, radiodyna-micsteering control 'of even date with this application,and inwhich rumenta plurality of mechanically tuned elements equipped with improved airvanes are arranged to make a positive jnon-vibrating electrical contactfor the control of steering mechanism under particular operatingconditions of the above mentioned instrument; the said instrument beingalso provided with means for indicating its operating characteristicsunderv various conditions to assure facility and convenience in use. i

Another object of the invention is to provide a selective relayarrangedto make a non-vibrating electrical contact by means of vibrating(reeds. I A still further object of the invention is to provide an airvane adapted for use on vibrating elements to develop unbalanced dynamicforces, and a to further provide a movably supported member having anaxis of rotation, and to which member .the dynamic forces developed bythe air vanes, and the .centrifugal forces developed by the ele-' mentsin vibration, ful torque around .the axis-of rotation of said member.

Another object of the invention is to describe methods for translatingconstrained mechanical vibrations into continuous and also differentialtorques of constant and also variable magnitudes which may be employedfor actuating various types of instruments and apparatus.

Other objects of the invention will be made ap- 45 parent inthe courseof. description.

A problem in the prior art has been the vibrating contact made by avibrating reed.

I have devised means to eliminate the vibratcontact and yet retain theselective advanposes, some damping may be required, and this is readilyaccomplished by the use of common forms of alr'vanes n xed on the freeends of the invention is to provide an in-.

are applied to produce a useto facilitate explanation of of a vibratingreedas shown in Figs. 3;

of Technol- 1 No; 478,498 v reeds. In operation these reeds with theirair dampers are wasteful of energy in two respects.- The centrifugalforce developed by, the reed in vibration is lost and the resistance ofthe air overcome by the movement of the damper vane is energy consumedand lost. In Figs. 3, 4, and 5 I illustrate a method of producing'andutilizing this otherwise wasted energy for useful purposes.

Fig. 1 in the drawing is a representation of a radio receiving device.

Fig. 2 illustrates the characteristics of the signals and thespatialarrangement of the zones of maximum amplitude of the directional 'sig-'nals, and also the zones of equal signal intensity of a doublemodulation. directive radio range 15 beacon.

Fig. 3 is a side view of a selective non-vibrating contact relay. J j

Fig. 4 is an illustration ofthe dynamic forces developed by areed invibration when having differently shaped air vanes attached atits freeend and also showing how these forces are combined and applied to acantilever to produce a useful torqueat its axis of rotation.

Fig. 5 is a projection of a selective diflerential relay embodying someof the features of this invention in an instrument for automaticallycontrolling the steering mechanism of vessels in accordance with thesignals received from a particular radio beacon at a given time. A pairof .30 reeds 'are provided for each beacon and several beacons areprovided for in the apparatus.

Fig. 1 shows a radio receiver at l comprising a tunable circuit at 2coupled to the antenna 3. and a switch "at l to tune the circuit 2. Atrans- 85 former 5 is arranged to pass the audio frequency output of thereceiverto the electro-magnetic unit 6 shown in Fig. 5. 4

Fig. 2 illustrates a directional radio range beacon in which a pair'ofdirectional antennas ll 40 and I! are arranged at an angle to oneanother Qi'or radiating waves modulated withbarticular and 85 cyclesrespectively theinvention. The

frequencies such as 65 equislgnal zones A, B, C, D, as definite courses,rangea orarbitrary lines of reference. However, since the functioning ofthe i apparatus may appear complex in some particulars, an understandingof the mode of operation of the system willbe aided ,byconsiderlng.

movements of the illustrated vessels more particularly with respect toor proximity of the vessels, to the one or the other of the zones ofmaximum signalintensity, rather than to consider the movements'oi' themaybe thought of the approach toward,

as of secondary importance.

60 forces' are effective 70 of rotation 42.

. bitrary lines of reference. The apparatus herein described is notlimited .to operationon the equisignal zones, and these zones are hereconsidered The description will be more'readily understood if it iscarried in mind that the course designator'66 associated with the panel61, Fig. 5 is always in the position shown in the drawing when the zoneof maximum 65 cycle signal intensity lies on the right-hand J side ofthe vessel, and this holds good on any heading of the vessel whethersteering toward or away from the beacon. The course designator 66 ischanged over to its second position only when the maximum 85 cyclesignal zone lies on the right-hand side of the vessel when heading on agiven course toward or away from the beacon.

Fig. 3 is a selective tuned reed or'resonance relay constructed inaccordance with my invention to eliminate the vibrating contacts commonto such instruments and is comprised of a lever 22 pivotally fulcrumedat 23 to, a supporting frame 24. A tuned reed 40, having an unbal- 25anced air vane 31 fastened to its free end, is

attached at its fixed end to one arm of the lever 22. The other arm ofthe lever 22 has attached thereon a spring 21 carrying a contact button28. An adjustable contact 29 is arranged ad- 30 jacent the button 29 tomake a solid contact therewithwhen the reed 40 is in vibration and theaerodynamic force developed by the unbalanced air vane 31 causes themovably supported member 22 to move from its initial position or initialposition of equilibrium as indicated by the dotted line 30, to itscontact making position shown bythe line 31. A tension spring 32 isarranged between the lever 22 and the frame 24 to assist in restoringthe movable member 22 to its initial position against the stop-rest 33in which position of the member 22 the contact between 28 and 29 isbroken. Due to the bending of the spring 21 the button 26 exerts a rubbing motionon the face of the contact 29 thereby tending to keep thecontact surfaces clean and of low resistance in the secondary'circuit34. One arm of the lever 22 constitutes the armature of theelectromagnet 35 in the'primary circuit 36.

Fig. 4 illustrates diagrammatically the dynamic forces developed by areed 49 having differently shaped vanes fixed to its. free end, andwhich forces are utilized in this invention. Differently shaped airvanes are shown at 31, 38 and These vanes are fixed to the reeds 40which form one side of the right-angled cantilevers M, Mn, and 4 I0which are arranged to rotate around an axis of rotation 42. The arrowsin the drawing show the direction in which the developed when the reeds40 are in a state of .vibration. Considering first the vane 31, when areed is in a state of vibration there is a centrifugal force developedwhich acts in the direction indicated by the arrow (0), or parallel thelength of the reed 49, or in other words, in a line parallel to the lineof position of equilibrium, and this force (a) exerts a tension at thefree end of the cantilever 4| to produce an effective and continuoustorque around the axis The vane shown at 31 is a semispherical cup incommon use on anemometers or wind speed indicators. y when the reed 40is in vibration and the vane 31 attached thereto is beating the air intwo directions, the air offers 7 a greater resistance to the concaveside ktthan to the convex side of the cup thus producing an unbalancedforce in the direction of the arrow 1), or tangent to the curvilinearmotion of translation of the vane around the axis of rotation 42. Theresultant force of the two applied forces a and b, or the turning momentof the cantilever 4|, is indicated by the arrow 31ab. At 38 is shown abalanced vane which beats against the same air resistance in bothdirections of its travel when the reed 40, to which it is attached, isin vibration. But owing to the fact that this vane 38 presents twoworking faces 1 and m, or inclined planes, to the resisting medium, anaerodynamic force is developed in the direction of the arrow d, orparallel to the length of the reed 40, and thus augments the centrifugalforce 0, the two forces tending to move the cantilever 4m in thedirection 380d. To utilize the three dynamic forces just explained Ihave combined the working faces-of the vanes 31 and 38 in the improvedvane shown at 39, 3911,11, and 1', and taken in combination with thereeds 40 and the cantilever 0, having an axis of rotation at '42,represents a novel feature of my invention. The vane 39 presents threeworking faces is, l, and m to the resisting medium when the reed 49 isin vibration. The vane 39 is preferably hollow and closed on all sidesand working faces except at k which is left open and produces the force(b) first considered in connection with the vane 31 and now identifiedby the arrows e and a in connection with vanes 39 and 39p. When the twofaces I andm, 39, are alternately driven against the air by the reed 40,the vane 39 exerts a tension in the direction indicated at ,f, orparallel to the length of the reed, and k which causes a resistance tothe movement of the reed 49 in only one direction of its travel,produces an unbalanced force in the direction e,'or in one directiontangentially to the are described by the free end of the reed 40. Itwill thus be obvious that the forces developed by the vane 39augmentedand the surfaces of the vanes will be streamlined I .where lowresistance is desired, and other advantages are to be gained thereby. I

The vanes 39 and 39p, also shownin 5 are identical in construction inevery particular but one. Since all the vibrating reeds in my apparatusare tuned to different frequencies, the vanes must also be differentlytuned as to size, shape, or weight to conform to the frequency at whichthey are designed to operate when attached to their respective reeds andthus develop resultant forces of the same magnitude as all the otherreeds and vanes in the apparatus. The value 39p develops aresultantforce of the same magnitude as that developed by the vane 39 whenthereeds 40 are vibrating with equal amplitude,

but the resultants of the forces developed by the of operation of theinstrument shown in Fig. 5.

If the'two reeds on the: cantilever 4H0 are vitensities of the signalsdetected by the The combined structure shown the featuresof the mallyrests on the insulation being provided for the positions of the contactstrips 49-58 under the The relative positions of the brating with equalamplitude, the forces developed by the reeds and their vanes are equaland opposite and the cantilever cannot rotate on its axis 42. Should thevibratory amplitude of one reed increase while that of the opposite reedis decreased proportionately, the forces acting on the cantilever wouldbecome unbalanced and rotation would ensue in one direction or the otheras indicated at '38efg and 381m. At 39r and 39q are two views of the newair vane, the shape of which is difficult to describe accurately.

The embodiment of the invention illustrated in Fig. comprises a pair ofbrackets 44 upon which the pivot spindle 42, supporting the cantilevermovement 4 0, ispivotally mounted, Two levers 8-8 constructed inaccordance with my invention are pivotally mounted at 9, on theright-angled cantilever movement He. The levers 8-8 havea plurality ofreeds 48 mounted on the short arms -|'3, all of said reeds having adiiferent period of vibration. One pairiof the reeds mounted on oppositesides of the movably supported member 0 are shown as having a tunedfrequency of 85 cycles and 65 cycles respectively for purposes ofexplanation in this description. Each of the reeds 48 has an unbalancedair vane at 39, and each of said vanes is designed to functionefliciently at the frequency to which its respective supporting reed ismechanically tuned. by the reeds 48, the levers 8-8, the frame 4|0, andthe pivot spindle 42, constitutes the balanced right-angled cantilevermovement diagrammatically illustrated at Mo, Fig. 4.

To the pivot spindle 42 is attached a spiral spring 45 for the purposeof maintaining and otherwise restoring. the movement 0 to its normalposition shown in the drawing when not actuated by unbalanced forcesdeveloped by the reeds 48 and their vanes 39. which actuate the reeds 48are transmitted from the electro-magnetic unit '6 to the long arms ofthe levers 8 by means of the armature rod 1, the pulsating currentsenergizing the unit 6 being derived from the receiver Fig. 1, throughthe transformer 5. The pivot spindle 42 carries an arm 46 which carriesa contact roller 41 which functions as a non-vibrating contact actuatedby vibrating reeds, and constitutes one of invention described inconnection with the structure shown in Fig. 3. Arranged under the rollerinsulating material 48 separating two metal contact strips 49 and 58which are operatively arranged on a movable bar 5|. The roller 41norrelay movement 4|o is acted upon by unbalanced forces, the arm 46causes the roller 41 to make contact with one or the other of thecontact strips 49-58 in accordance with the relative inreceiver I,Fig. 1. 'The movable bar 5| forms a rack which is engaged by a pinion 52which is operated by the thumbscrew 53, the thumbscrew 53 purpose ofadjusting the contact roller 41. contacts 89-58, under thecontact-roller 41, with respect to the operating positions of themovable member 4|o and its contact making arm 46, are indicated on thedial 15. A dial pointer 54 is pivotaily connectedat 55 to the movablebar 5| for the purpose of indicating on the dial '15 the differentialoperating relation between the fixed at its free end as shown Thepulsations The wire 18 leading to 41 is shown a piece of 48, but whenthethe gyro-pilot system is not a vention, its mechanism has not beenshown in position by the guide 59. The reason for employing a movablefulcrum 58 working in a slot 51 is to allow a reversal in the relativemovements of the pointer 54 and the bar 5| When the fulcrum 58 is at thebottom of the slot 51 and below the pivot support 55 the pointer 54 willmove in the same direction as the bar 5|. But when the fulcrum 58 isat'the top of the slot 51 and above the pivot support 55, the pointer 54will move in av direction opposite to that of the bar 5|. This reversalin the relative movements of the pointer 54 and the bar 5| is necessaryunder certain operating conditions of the apparatus. The movable fulcrum58 is connected by a rack 68 with a gear 6|, and which gear engages arack 62 on connecting rod 63. The rod 63, which is also operativelyconnected to the relay reversing switch 65, forms another rack 64 whichis engaged by a manually operated gear and course designator 66. Thepanel61 with which the dial pointer or course designator 66 isassociated is designed to identify the various radio ducing equisignalzones fixed in azimuth. The dial shown at 15 indicates the number ofdegrees or angular distance that a vessel is maintaining a course to theright or left of a particular course or equisignal zone identified onthe panel 61, taking alsointo account the fact that the vessel isproceeding to or from the beacon. The contact segments 49-58 areconnected by circuit wires 68 and 69 to the relay reversing switch 85and then by circuit wires 1| and 12 to the primary relays on the relaypanel 13 and from which panel the steering motor of the vessel iscontrolled through the circuit wires 14.

movable contacts 49-58 and the other movable double modulation type ofdirective radio beacon arranged for pro-' relay panel 13 is neutral toboth circuits 68 and 69.. The function of the reversing switch is toreverse the order of actuation of the primary relays on the panel 13which are actuated through the circuits 68 and 68 by the closing of 'thecontacts 49 or 58 by the contact roller 41. If now the gear 66 be turnedclockwise in direction, the bar 63 will be moved to the right thus alsooperating the switch 65 and reversing the circuit arrangement betweencontacts 49-58 and the two relays connected to wires 1I-12. The relaypanel 13 is a conventionally arranged panel in common'use with a wellknown type of automatic pilot steering mechanism for ships and which iscontrolled by the gyroscopic compass. The roller 41 in my apparatustakes the place of the repeater motor contact roller in the gyropilotsystem above mentioned 49-58 in my apparatus take contact .rings in thegyro-pilot the place of the system, but since part of this inthe drawingbeyond the relay panel connections 14.

and the contacts 'Fig. 2, and designated by The pair of reeds designatedas having periods of 85 cycles and 65 cycles, respectively, are mountedin opposed operating relation in the differential relay Fig. 5, and aretuned to the modulation frequencies of a particular beacon in a systememploying several of such beacons. When the audio frequency output ofthe receiver l energizes the electro-magnetic unit 6 through thetransformer 5, the armature rod 1 actuates the levers 8, and the 85cycle and 65 cycle reeds carrying the air vanes 35 are set in vibration.If a vessel equipped with this apparatus is proceeding toward the beacon'on the equisignal zone or radio course A, as illustrated by the vesselIt, the dial pointer 56 on the panel 6'5, the instrument will functionin the following manner. If for example the vessel Ill remains exactlyon the equisignal zone'or course A, the 65 and 85 cycle reeds willvibrate with equal amplitudes and as heretofore explained, theirtensions on the cantilever ilo will be of equal magnitude and inopposite directions, while the contact roller ll will remain upon theinsulation is and the relays on the relay panel 13 will not be actuated.If the vessel should move to the left of the designated course asillustrated at H, Fig. 2, the vessel would be moving toward the side ofthe equislgnal zone where the 85 cycle signal strength predominates andwith the result that the 85 cycle reed will increase its vibratoryamplitude, while the 65 cycle reed will proportionately decrease itsamplitude, in consequence of which the roller i? would be moved on tothe contact segment 50. The .circuit arrangement between the contactstiland the relays on the panel I3 is such, with the switch 85 in itspresent position, that when the roller M makes. contact with the contact50, the rudder of the vessel is automatically turned to the right or ina direction opposite to the movement of the roller 47. The rudder inthis position will restore the vessel to its designated course on theequisignal zone, and when on the equisignal zone, the 85 and 65 cyclereeds will again be vibrating with equal amplitude and the retractilespring will assist in restoring the roller 51 to its initial posidegreest .while proceeding away from the beacon, as illustion on the insulation48. If the vessel moves to the right of the course as roller 61 willmake contact with d9 due to the tension of the 65 cycle reed whichincreases its amplitude when the vessel moves to the right of theequisignal zone. With the circuit 69-79 closed, the rudder moves to theleft or opposite to the movement of the roller contact M and the vesselis again'restored to its designated course where the intensity, thereeds vibrate with equal amplitude, and the roller 41 is restored to itsinitial position on the insulation it. It will thus be obvious that theselective differential control apparatus steers the vessel automaticallyby the directive radio beacon signals If it should be desired tomaintain a course 10 ithe right of the equisignal zone C, and

tr'ated at I5, the thumbscrew 53, which is pro- .vided for the purposeof setting courses at different angular'distances around the beacon,will be turned to the left or counterclockwise, thus moving the contactsupport 5! to the right thereby bringing the contact 50 under the rollerM, and the dial pointer or angular distance indicator 5% will have moved10 degrees tothe right, thereby indicating the course which will beautomatically maintained. The course designator 66 is in the Iillustrated at 12, the

beacon signals are received with equal correct position as shown in thedrawing for this heading of the vessel since the maximum 65 cycle signallies on.the right-hand side of the vessel 15 when heading away from thebeacon. If, for example, the vessel were made to steer an oppositecourse toward the beacon on course C, the cycle'maximum signal zonewould then lie on the right-hand side of the vessel, and the coursedesignator 66 'would have to be changed over in order to designate Tobeacon, Course C on the panel Bl to permit proper functioning of thesteering control apparatus. As heretofore explained, the contact roller4'! when resting on the contact 50 closes the circuit 68-48 and causesthe rudder to be turned to the right. With proper adjustment of theapparatus the vessel will maintain a course 10 degrees to the right ofthe equisignal zone C. It will be understood that the degree of movementof the rudder is purposely limited; and the course will be automaticallyaltered or corrected only a small amount at a time by means and methodswell known and understood in the art. At 10 degrees to the right of theequisignal zone C the 65 cycle reed will have suificiently increased itsvibratory amplitude to move the roller 4'! to the insulation 68 and inwhich position the rudder will be automatically restored to its neutralposition by the relays on the relay panel I3. Any movement of the rollercontact to the right or left will be met by the rudder moving in theopposite direction and restoring the vessel to its designated course.

If now, for example, the vessel at I6 is made to steer a course awayfrom the beacon, on equisignal zone B, it will be found that therelative positions of the differently characterized zones of maximumsignal intensity are transposed with respect to the heading of thevessel, that is to say, where formerly the 65 cycle maximum signal layon the right-hand side of the vessel, the 85 cycle maximum signal nowlies on the right-hand side of the vessel. This ambiguous relation ofthe transmitted signals with respect to the headings of a vessel ondifferent beacon courses and in different directions on the courses, toor from the beacon, has been provided for by means of the change-overmechanism shown at 56 which designates the proper setting of theinstrument for steering a course to or from the beacon, by the reversingswitch 85, and by the movable fulcrum 58 working in the slot 57 forreversing the relatitve movement of the pointer 55. This reversal of theorder of actuation of the-relays on the panel 13 by the circuit closingcontacts 49, 56, and 51 can be carried out by other means such as wouldconsist of a simple mechanical move ment for reversing the position ofthe contacts 49 and 50 and eliminating the reversing switch '55, and itis to be understood that such modifications suggesting themselves tothose skilled in the art are within the scope of my invention.

Considering again the case in which the vessel I6 is heading away fromthe beacon on courseB, if the course designator 66 is not changed overto indicate From beacon, Course B, on the panel 61, the automaticsteering apparatus will cause the vessel to execute a 180. degree turnfrom its course away from the beacon and will thereafter steer itselfback toward the beacon as shown at H. When the course designator 66 ismoved to the right, the connecting rod 63 operates the reversing switch65 and. also the gear 6| whichmoves the fulcrum '58 to the top the. slot51 in the position of the fulcrum 58 in the slot 51 reverses the same inpractice.

the movement of the pointer 54 relative to the movement of the rack 5|.

It will be apparent that this embodiment of the I invention requires notechnical knowledge on the part of'the navigator for an intelligent useof The relative positions of the principal radio courses are known tothe navigatorand the ambiguous relation of the transmitted signals onthe various courses is provided for in the apparatus.

It is to be understood that the invention is not limited to any specificconstruction but might be embodied in various forms without departingfrom the spirit of the invention or the scope of the appended claims.

Having described my invention what I now claim is:

1. In a navigational apparatus adapted for cooperation with a source ofdifferently characterized signals to delimit definite courses, thecombination including a receiving device, a selective differential relayconnected to said receiving device and arranged to respond to therelative magnitudes of said signals, a contact maker associated withsaid relay, a set of adjustable contacts ar ranged adjacent said contactmaker, means to adjust the operating relation between said adjustablecontacts and said contact maker, and automatic steering apparatuscontrol circuits arranged with said contacts for differential actuati'onthereby.-

2. In apparatusaccording to, claim 1, in which an indicating means isoperatively arranged to indicate the degree of adjustment of theadjustable contacts relative to the position of the contact maker.

3. In apparatus according to claim I, in which a course designator isoperatively arranged with the steering apparatus control circuits fordesignating and determining the proper operating adjustment of the relaycontrol apparatus for operation on a given course.

4. In apparatus according to claim 1, in which a course designator; ameans for indicating the degree of adjustment of the adjustablecontacts, together with means for reversing the order of movement ofsaid indicating means; and means for reversing the order of control ofthe steering apparatus control circuits, are operatively associated forsimultaneous adjustment of the relay control apparatus for operation ona given course. 5. In navigational apparatus adapted for use with asource of differently characterized signals producing equisignal zonesfixed in azimuth, the combination comprising automatic steering controlapparatus simultaneously and differentially responsive to said signalsand operatively arranged with steering mechanism on a movable body forcausing the latter to maintain a predetermined course relative to agivenequisignal zone, course setting means to make said steering controlapparatus respond to predetermined relative magnitudes of said signalsto cause said movable body to maintain a predetermined course at apredetermined angular distance tothe right or left of said equisignalzone, and means to indicate and determine the angular distance of agiven course to the right or left of said equisignal zone.

6. In apparatus as defined in claim 5, in which means is associatedwith-the steering control apparatus to identify the various equisignalzones and designate the proper adjustment of said control apparatus formaintaining a given course on a given equisignal zone in a givendirection relaratus connected to said work circuits.

tive to the direction of the source of signals pro ducing said zones. Y

7. In apparatus as defined in claim 5, in which reversing means for theangular distance indicating means; means for reversing the order of theoperating control of the steering control apparatus; and designatingmeans, are operatively associated with the steeringrcontrol apparatus.

8. In automatic steering control apparatus, a receiver of differentlycharacterized simultaneous signals, an electro-mechanical resonancedifferential control device operable responsive to the frequencies andrelative magnitudes of said signals, and automatic steering apparatuscontrol circuits operatively associated with said control device fordifferential actuation thereby.

9. A mechanically selective differential device operative in response tothe relative magnitudes of a plurality of simultaneously appliedactuating forces, consisting of a movably supported mem her, aplurality-of vibratile elements arranged in opposed operating relationwith said member for causing the latter to move differentially, meansfor causing said elements to vibrate, and apparatus operativelyassociated with said member for actuation thereby.

10. A selective differential control device comprising a movablysupported member, a plurality of differently tuned vibratile elementsarranged in opposed operating relation with said member and adapted fordeveloping centrifugal forces which actuate said member, means to causesaid elements to vibrate, and desired apparatus operatively associatedwith said member for actuation thereby.

11. The combination comprising a movablyv supported member, a pluralityof vibratile elements arranged in opposed relation integrally with saidmember to cause the latter to move differentially when the opposedactuating forces developed by said elements are unbalanced, means tocause said elements to vibrate, and work circuits operatively associatedwith said member for differential actuation thereby.

12. The combination comprising a movably supported member, a pluralityof differently tuned vibratile elements providedwith unbalanced vanesoperatively arranged in opposed relation with said member ferentialmovement thereof, means to cause said elements to vibrate, and apparatusassociated to'effect a resultant difing frequencies corresponding to thefrequency of vibration of said reeds, contact making means associatedwith said member and arranged to make contact differentially with aplurality of contacts adjacent said contact making means a plurality ofwork circuits connected to said contacts and said contact making means,and appa- 14. A differential device which responds difference inmagnitude of a plurality of neously received signals, comprising a ofvibratile elements for producing to the simultaplurality dynamic forcesacting in opposition on a balanced rotary movement, means to actuatesaid elements selectively, circuit actuating means co-operating withsaid rotary movement for actuating a set of control circuits, andapparatus connected to said control circuits to be actuated thereby.

15. In combination, a craft equipped with suitable automatic steeringapparatus, control means mechanically selective and differentiallyresponsive to a plurality of received signals and operatively associatedwith said steering apparatus, and course setting means associated withsaid responsive control means for the purpose of regulating the functionof said control means whereby the steering apparatus is made to respondto desired difierences in strength of said received signals to causesaid craft to automatically maintain selected courses ranging indifferent desired directions.

16. In automatic steering apparatus for a movable body, comprising meansfor receiving and detecting radio signals, control means mechanicallyselective and differentially responsive to the distinctive modulationcomponents of said signals, course indicating means associated with saidcontrol means, and steering mechanism for said body controlled by saidcontrol means.

17. Steering apparatus for a movable body, comprising a radio receiverfor supplying two simultaneous currents of difierent frequencies andhaving relative magnitudes which'vary in accordance with the course ofthe body, a mechanical resonance difierential control device responsiveto the frequencies and magnitudes of said currents, and steeringmechanisms for said body controlled by said control device.

18. A selective relay, comprising, a movably supported member, vibratileaerodynamic means arranged with said member for causing the latter tomove, means for causing said vibratile means to vibrate, and apparatusoperatively associated with said member for actuation thereby.

19. A selective relay, comprising a movably supported member, a tunedvibratile element having an unbalanced vane operatively arranged withsaid member for causing the latter to move, primary means for causingsaid element and vane to vibrate, and secondary means associated withsaid member for actuation thereby.

20. The combination including a plurality of vibratile elements forproducing dynamic forces acting in opposition on a movable member, meansfor actuating said elements selectively, means cooperating with saidmovable member for differentially actuating a plurality of controlcircuits, and means for altering and indicating the relative operatingadjustment member and said control circuits.

THEOPHILE E. BROCKSTEDT.

between said movable-

